feat: add Alibaba Cloud Coding Plan support

Add support for Alibaba Cloud Bailian Coding Plan, a coding-focused AI service
that provides fixed monthly pricing for multiple models.

Changes:
- Add alicloud provider with OpenAI-compatible API endpoint
- Support 8 models: qwen3.5-plus, kimi-k2.5, glm-5, MiniMax-M2.5,
  qwen3-max, qwen3-coder-next, qwen3-coder-plus, glm-4.7
- Use "ali" as provider alias (ali/model format)
- Add API key validation and connection testing
- Add frontend provider definition with "ALi" text icon

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/api/providers/[id]/models/route.js

@@ -71,6 +71,14 @@ const PROVIDER_MODELS_CONFIG = {
     },
     authHeader: "x-api-key",
     parseResponse: (data) => data.data || []
+  },
+  alicloud: {
+    url: "https://coding.dashscope.aliyuncs.com/v1/models",
+    method: "GET",
+    headers: { "Content-Type": "application/json" },
+    authHeader: "Authorization",
+    authPrefix: "Bearer ",
+    parseResponse: (data) => data.data || []
   }
 };